Cosmetically the white skin with little pigmentation, speckle, or freckle appears to be favored, for this reason a substance having a skin whitening effect and very safe even when used for an extended time is in demand.
The pigmentation, speckles, freckles, and the like, are generally considered to be caused as a result of the melanin production enhanced by the activated melanocyte present in the skin due to the stimulation from skin exposure to ultraviolet ray, hormonal imbalance, genetic factors, or the like. The mechanism of melanin production enhancement is complicated but it is known that melanin is biosynthesized by the enzyme tyrosinase activity and the dopa oxidase activity of tyrosinase is deeply involved with the melanin production mechanism (Non Patent Document 1).
Skin whitening agents targeting this melanin production mechanism have been developed. For example, ascorbic acid, arbutin, kojic acid, and the like, have been reported as skin whitening agents having an effect for inhibiting the melanin production by inhibiting the enzyme tyrosinase activity (Non Patent Document 2).
Further, plant extracts having a skin whitening effect and inhibiting the dopa oxidase activity have been reported. Examples include toosendan (Melia toosendan Sieb. et Zucc.), souka (Amomum tsao-ka Crevost et Lemaire), seneshio gurashirisu (Senecio gracilis) and kokurirc (Veratrum nigrum L.) (Patent Document 1), garden angelica (Angelica archangelica), flowering dogwood (Benthamidia florida), kansui (Euphorbia kansui Liou), Japanese sumac (Rhus chinensis Mill.), okazeri (Cnidium monnieri (L.) Cuss.), hairvein agrimony (Agrimonia pilosa Ledeb.), rouro (Diuranthera minor (C. H. Wright) Hemsl.), and common barberry (Berberis aristata) (Patent Document 2), inukaramatsu (Pseudolarix amabilis), true indigo (Indigofera tinctoria) and devil's trumpet (Datura metel) (Patent Document 3), and pomegranate (Punica granatum) flower (Patent Document 4).
However, a more effective skin whitening agent is expected to be developed.
Haguro-so (Peristrophe japonica) is a plant belonging to the Family Acanthaceae, Genus Peristrophe. A composition comprising plants belonging to the Family Acanthaceae including Genus Peristrophe is known for preventing and ameliorating metabolic syndrome (Patent Document 5). However, it is not known that these plants have skin whitening effects, melanin production inhibitory effects, or dopa oxidase activity inhibitory effects.
Arylnaphthalene lignans are known to be isolated from plants such as Haplophyllum patavinum or Cleistanthus collinus (Non Patent Documents 3 and 4). As the physiological activities rendered by arylnaphthalene lignans, justicidin A, justicidin B, diphyllin, and tuberculatin are known to have bone resorption activity, antiviral activity, or antitumor activity (Non Patent Documents 5 and 6) as well as justicidin A and cleistanthin A are known to have antitumor activity (Non Patent Documents 7 and 8, and Patent Document 6), and the like. However, it has not been known that these and other arylnaphthalene lignans have skin whitening effects and melanin production inhibitory effects.